The Canadian Flag On Your Back Pack

When Americans travel in Europe, do they really stitch a Canadian flag into their back pack and pose as Canucks? I've often heard about this and yesterday on "The Simpsons" Lisa did just that before their trip to Italy. Is this practice merely an urban legend or does it actually happen?

A little Googling proves this is very common advice given to Americans who are worried they'll be mistreated because they're American. Many give this advice and speak of people they know who did this with much success, but there are few first hand reports from people who have done this. Now that the sewing of a Canadian flag on one's back pack has been immortalized by the Simpsons, I want proof that people actually do it and I want to know if it actually makes a difference.